Multicolor dye developer systems

ABSTRACT

Photographic elements wherein at least two adjacent imageforming units (each comprising silver halide and dye developer) are separated by an alkali-permeable, water-insoluble stratum of a polyvalent metal salt and a film-forming, alkali-permeable, water-soluble polymer having free carboxylic acid groups, are processed in the presence of a material that is a chelating agent for the polyvalent metal, the chelating function of said material being destroyed imagewise in just exposed areas as a function of development.

United States Patent US. Cl 96/3 96/29, D, 96/77 lnt.Cl G03c 5/54, G03cl/40 Field of Search 96/29 D, 3, a 76, 77

Reterences Cited UNITED STATES PATENTS 3,196,015 7/1965 Ryan 96/29Inventor Paul H. Stewart Rochester, N.Y.

Appl. No, 797,283 Filed Feb. 6, 1969 Patented Nov. 2, 1971 AssigneeEastman Kodak Company Rochester, N.Y.

MULTICOLOR DYE DEVELOPER SYSTEMS 16 Claims, No Drawings OTHER REFERENCESMartell, A. E. and Calvin, M., Chemistry of the Metal Chelate Compounds,Third Printing (1956); Prentice-Hall, Englewood Cliffs, N. 1., Pages134- 138 and 556.

Primary Examiner-Norman G. Torchin Assistant ExaminerAlfonso T. SuroPicoAtt0rneys-W. H. J. Kline, J. R. Frederick and O. H. Webster ABSTRACT:Photographic elements wherein at least two adjacent image-forming units(each comprising silver halide and dye developer) are separated by analkali-permeable, waterinsoluble stratum of a polyvalent metal salt anda film-forming, alkali-permeable, water-soluble polymer having freecarboxylic acid groups, are processed in the presence of a material thatis a chelating agent for the polyvalent metal, the chelating function ofsaid material being destroyed imagewise in just exposed areas as afunction of development.

MULTICOLOR DYE DEVELOPER SYSTEMS The present invention relates to theart of photography, and more particularly, to multicolor dye diffusiontransfer systems utilizing dye developers.

' Compounds which contain in the same molecule both the chromophoricsystem of a dye and a photographic silver halide developing moiety havebeen described in the photographic art as useful compounds inphotographic'elements for preparing color images by diffusion transferprocesses. Such compounds are'commonly called dye developers".Photographic elements containing such dye developers generally comprisea plurality of photosensitive silver halide emulsions wherein each ofthe emulsions is selectively sensitized to a different region of thespectrum. A dye developer is positioned contiguous to the silver halidein each of such emulsions, the dye developer more generallybeingsubstantially complimentary in color to the color of light recordedin the contiguous silver halide. Such a photoelement is processed withan alkaline composition. The latent image is developed in the negativeimage areas with the dye developers, this development immobilizing thedye developers in such negative image areas. The dye developers in theunexposed areas diffuse to the surface imagewise and are transferred toa reception layer or receiving sheet to form a positive multicolorimage. Such color diffusion transfer processes are disclosed in U.S.Pats. Nos. 2,983,606, 3,253,915, British Pat. 804,971, and French Pat.1,313,767, as well as elsewhere in the literature.

Ideally, each dye developer should develop only contiguous silverhalide, to wit, the cyan dye developer should develop only thered-sensitive silver halide emulsion layer, the magenta dye developershould develop only the green-sensitive silver halide emulsion layer,and the yellow dye developer should develop only the blue-sensitivesilver-halide emulsion layer in a conventional three-color system.However, in practice, each dye'developer has been found to develop to anundesirable extent each silver halide emulsion layer. The result of thiseffect is to produce color contaminationand'desaturation of colors inthe transfer printspred in particular being a color of relatively poorquality. Conventional interlayers or barrier layers between each of thecolor-formingunits of such materials as gelatin have been utilized, suchlayers, however,'only beingeffective to a limited degree-in improvingthe interimage characteristics in multicolor dye developer diffusiontransfer systems.

Becker U.S. Pat. No. 3,384,483, issued Mar. 25, 1968, describesphotographic elements useful in preparing multicolor dye developerdiffusion transfer images containing certain alkali-permeable,water-insoluble salt strata or barrier layers between thesilve'r halideemulsion layers that can be utilized to reduce color contamination ofthe transferred images. However, such barrier layers tend to preventsome of the soluble image-forming dye developer in underlying layers,particularly cyan dye developer, from diffusing to the receivingsheet'for the multicolor dye developer images, thus resulting in loweredDmax in the transferred image for the undercoated dye developer.

An improvement was found in photographic elements having barrier layersof the type described in Becker U.S.Pat. No. 3,384,483. Theimprovemenywhich is described by Becker in Belgian Pat. 708,491 issuedJan. 31, 1968, features the use of an organic sequestering agent for thepolyvalent metal of the barrier. The sequestering agents describedtherein substantially uniformly increase the'permeability of the barrierto underlying dye developer. This results in improved-color saturation,although color contamination is increased.

It would be highly desirable to provide an improvement in dye developersystems utilizing a salt stratum of the type described in Becker U.S.Pat. 'No. 3,384,483 whereby the salt stratum could be renderedmore'permeable to dye developers iri just the unexposed areas. Such animprovement would result in good diffusion of dye developers fromunexposed areas, while effectively inhibiting undesired diffusion of dyedevelopers from exposed areas.

It is an object of this invention to provide novel photographic elementsuseful for preparing multicolor dye developer diffusion transfer imageshaving high color saturation as well as low color contamination.

It is another object of this invention to provide novel photographicelements particularly useful for preparing multicolor dye developerdiffusion transfer images having high red saturation as well as low redcontamination.

It is still another object of this invention to provide a new method forpreparing multicolor dye developer diffusion transfer images having highcolor saturation as well as low color contamination utilizingphotographic elements containing alkali-permeable, water-insolublestrata of a polyvalent metal and a polymeric carboxylic acid positionedbetween at least two of the dye image-forming units of such elements.

These and other objects of the invention are accomplished withphotographic elements comprising a support having coated thereon (l atleast two dye image-forming units composed of a light-sensitive silverhalide emulsion and a dye developer contiguous to silver halide of theemulsion, and (2) an alkali-permeable and water-insoluble stratum orbarrier, layer of a polyvalent metal salt of a film-forming, alkali--permeable, water-soluble polymeric carboxylic acid positioned betweenat least two of the dye image-forming units, such stratum being lesspermeable to dye developers in aqueous alkaline solution than thepolymeric carboxylic acid used to prepare the salt stratum. Suchphotographic elements are described in Becker U.S. Pat. No. 3,384,483,issued Mar. 25, 1 968. In accordance with the present invention, the

processing of such photographic elements is carried out in the presenceof a material that is chelating or sequestering agent for thepolyvalentmetal moiety of the salt stratum, the chelating function ofsaid material being destroyed imagewisein just exposed areas as afunction of development. The material thus increases permeability of thebarrier layer in just the unexposed areas.

The chelating materials employed in this invention can beinitiallyprese'nt int'he llght sensitive photographic element, in theprocessing composition or in the dye developer image receiving element.

the barrier strata'in the unexposed areas, rendering the barrierpermeable to underlying dye-developer after such dyedeveloper hasdeveloped exposed silver halide contiguous thereto. in exposed areas,the catechol is an auxiliary developer, as shown in my copending U.S.Pat. application Ser. No. 676,603, filed Oct. 19, 1967, and nowabandoned. This invention results in color'prints havinghighcolorsaturation and low colorcontamination.

Any catechol can be used in the practice of this invention whichchelates the polyvalentmetal moiety of the salt stratum barrier layerand which is a silver halide developing agent. The catechols arepreferably colorless and soluble in the alkaline processing solution.The word catechol" is used generically herein to includel,2-dihydroxybenzencs, which can contain additional hydroxyl groups,such as a 1,2,3-trihydroxybenzene, a 1,2,4-trihydroxybenzene or a1,2,3,4,Stetrahydroxybenzene. Suitable catechols include those havingthestructural formula:

wherein: R R R and R can be hydrogen, an alkyl radical, preferably ofabout I to 8 carbon atoms (e.g., methyl, ethyl, propyl, butyl, amyl,hexyl, heptyl, octyl, etc.,), an aryl radical (e.g., phenyl, tolyl,naphthyl, etc.), hydroxyl, aryloxy such as phenoxy, halogen such aschlorine or bromine, carboxy or R and R or R and R when taken togetherwith the carbon atoms to which they are attached, represent the atoms tocomplete a eycloalkyl group containing from 4 to 6 carbon atoms (e.g.,eyclohexyl, cyelopentyl, etc.) which can contain an endomethylene group(e.g., methanocyclohexyl, methanocyclopentyl, etc.). Salts and esters ofthese eateehols can also be used.

A preferred class of catechols having the aforesaid structural formulaare those in which R,, R R and R, are either hydrogen or an alkylradical of from 1 to 8 carbon atoms.

Examples of suitable catechols include:

cateehol 4-methylcatechol 4-isopropylcatechol 3-isopropylcatechol4tert-butylcatechol 4phenylcatechol 3,6-dimethylcatecholl,2dihydroxy-5,8-methano-5,6,7 ,8-tetrahydronaphthalene hexoylcatechol1,2,3-tfihydroxybenzene 3-phenylcatechol 4ectylcatechol 4| octylcateeholl ,2,4-trihydroxybenzene p-ehlorocatechol 4,54libromocatecholl,2,4,5-tetrahydroxybenzene 4-phenoxycatechol The amount of chelatingmaterial utilized in the invention can be widely varied, the amountvarying with such variables as the number and type of barrier layers ofpolyvalent metalpoly earboxylic acid salt in the photographic element,the amount of polyvalent ion present in the system, the particularchelating material, the processing time, the particular positioning ofthe material in the system, the use of other auxiliary developers andrelated variables. Sufficient chelating material should be used toincrease permeability in just unexposed areas. When cateehol isemployed, typical useful concentration ranges are about I to I50 mg. ofcateehol per square foot when utilized in the light-sensitive element,about 50 to 200 mg. of cateehol per square foot when utilized in the dyedeveloper image receiving sheet or layer, and about 0.1 to percent byweight of the alkaline processing composition when utilized therein.Good results are obtained when a cateehol is the only chelating orsequestering agent present during processing.

The chelating material can be coated in combination with otherconstituents in the present photographic elements and image receivingsheets, or it can be coated in separate layers. The chelating materialcan be coated in an organic hydrophilic colloid as an aqueous coatingmelt. Likewise, the chelating material can be dissolved in ahigh-boiling (e.g., greater than l75 C.) solvent and dispersed in finelydivided droplets in a hydrophilic colloid and the resulting dispersioncoated.

The salt strata or barrier layers utilized in the subject dye developerdiffusion transfer system can be prepared with a variety of polyvalentmetal salts and polymeric carboxylic acids. The subject salt strata canbe formed on the element by coating a solution, on a water-permeablesubstrate, containing the polyvalent metal in water-soluble form on apolymeric carboxylic acid layer previously coated on the element to forma thin layer of a water-insoluble salt. The polyvalent metal inwater-soluble form can be coated directly on silver halide emulsionlayers if the vehicle for the silver halide is a polymeric carboxylicacid that forms a water-insoluble salt with the polyvalent metal moiety.lnterlayers of water-permeable materials can be utilized on either sideof the subject water-insoluble salt strata. Such salt strata arepreferably utilized between the magenta and cyan dye image-forming unitsto particularly improve red purity and saturation of the transferred dyedeveloper images. Similarly, the subject salt strata can be utilizedbetween the yellow and the magenta dye image-forming units as well asbetween both the magenta and the cyan dye image-forming units to improvecolor purity and saturation of the transfer dye developer images.

A wide variety of film-forming, alkali-permeable, watersoluble polymericcompositions containing free carboxylic acid groups, and includingwater-soluble salts thereof, can be utilized to form the subject saltstrata with polyvalent metal moieties. Typically, such polymers containabout 5 percent to 60 percent by weight of polymer of free carboxylicacid groups (i.e., available for reaction with the subject polyvalentmetal moieties in aqueous alkaline solutions) or the equivalent weightof water-soluble salts thereof. Typical of such suitable acid polymersinclude:

1. natural occurring carboxylic acid group-containing polymers andderivatives thereof including such proteins as gelatin, casein and thelike,

2. natural occurring high molecular weight carboxylic acidgroup-containing polysaccharides and derivatives thereof such as alginicacid, pectic acid, tragacanthic acid, carboxymethyl cellulose, and thelike, and

3. synthetic linear polymers containing carboxylic acid groups such asaddition vinyl polymers and condensation polymers wherein the monomericrepeating units are connected with such groups as O 0 0 ll j] H ll 7 ll-O, OCO, O. CNH, O(Jr\H, -NHCNH and the like, illustrative of suchsynthetic polymers are dis closed in US. Pat. No. 2,565,418, US. Pat.No. 3,062,674, US. Pat. No. 3,007,901 and British Pat. No. 886,882 andinclude succinoylatcd polyvinyl alcohol, maleic acid-styrene polymers,alkylacrylate-acrylic acid polymers, formaldehydesalicylic acidpolymers, acidic polyesters, acid polyamides and the like.

Polyvalent metal moieties are utilized to form the present salts as suchmoieties can be used to cross-link carboxylic acid moieties of thepolymeric carboxylic acid to form the present strata which have theproper degree of alkali permeability and water-insolubility to serve asbarrier layers to prevent color contamination and interdevelopmentbetween dye imageforming units. A wide variety of polyvalent metalmoieties can be utilized in preparing the subject salt strata. Suitablepolyvalent metals with which suitable salt strata of the invention canbe prepared include alkaline earth metals, such as calcium, barium andstrontium, and the like polyvalent metals that form alkali-permeable,water-insoluble salts with the above-described polymeric materialscontaining carboxylic acid groups.

The amount of polymeric salt utilized in the subject salt strata can bewidely varied, the amount varying with the effect desired and the natureof the polyvalent metal and the polymeric carboxylic acid. Moregenerally, the amount or coverage of the polyvalent metalpolymericcarboxylic acid salt stratum utilized is that which is substantiallyequivalent in permeability to dye developers in aqueous alkalinesolution to the calcium alginate formed when a stratum consistingessentially of sodium alginate is reacted with calcium chloride coatedthereover at a coverage of about 5 to mg. per square foot.

Typical alkali-permeable water-insoluble salts comprising the barrierlayers of the light-sensitive photographic elements used in theinvention include:

strontium gelatinate,

barium gelatinate,

calcium pectinate,

calcium alginate,

calcium-succinoylatcd polyvinyl alcohol,

calcium-polyacrylic acid,

barium alginate,

7 magnesium alginate,

strontium alginate,

calcium-condensation of formaldehyde and salicylic acid, and the like,and including mixtures thereof.

Dye developers are well known in the photographic art. Such compoundsfunction both as a silver halide developing agent and as a dye inphotographic difiusion transfer system's. Dye developers arecharacterized as being relatively nondiffusible in colloid layers suchas the hydrophilic organic colloids used in photographic emulsions atneutral pH, but diffusible in the photographic elements in the presenceof alkali ne processingsolutions. Generally, such dye developers aresubstantially insoluble in water, which property usually necessitatesthe use of organic solvents to incorporate the dye developers into theorganic colloid layers of the photoelements. The dye developers areparticularly characterized as containing both a chromophoric ordyemoiety and at least one moiety having a silver halide developing agentfunction. Particularly useful dye developers are those wherein thechromophoric moiety is an azo or anthraquinone d'ye moiety and thesilver halide developing moiety is a benzenoid moiety such as ahydroquinonyl moiety.

Representative dye developers of use in the dispersions of the inventionhave the general formula MN==N-D in which M is an aromatic orheterocyclic ring or ring system such as a benzene, napthalate,tetralin, anthracene, anthraquinone, pyrazole, quinoline, ,etc., ringwhich can be substittuted with such groups as hydroxyl, amine, keto,nitro, alkoxy, aryloxy, acyLalkyIamido, alkylaryl, carboxamido,sulfonamide, carboxyl or sulfo groups. D represents a silver halidedeveloping agent moiety imparting the developing agent function to thedye developer such as a hydroquinonyl group which can be substitutedwith amino, alkylamino, alkyl, hydroxyl, alkoxyl or halogen groups.

Typical useful dye developers are described in columns 9l3,of US. Pat,No 3,146,102, as well as elsewhere in the patent literature, including:Australian 220,279; German 1,036,640; British 804,971 and 804,973-;Belgian 554,935; French 1,168,292; and Canadian 557,021 and 579,038.

In the photographic elements of the invention, the dye developers arepreferably incorporated in hydrophilic organic colloidal vehicles orcarriers comprising the layers of the photographic element dissolved inhigh-boiling or crystalloidal solvents and dispersed in finely divideddroplets. in preparing such dispersions of dye developers, high-boilingor substantially water-immiscible organic liquids having boiling pointsabove about 175 C. are utilized. The high-boiling solvent can be usedalone in dissolving the dye developer and in forming the dispersion orit can be mixed with a low-boiling organic solvent e.g., boiling atleast 25 C. below the boiling point of the higher boiling solvent), or awater-soluble organic solvent, as an auxiliary solvent to facilitatesolution of the dye developer. A preferred range of proportions ofhigh-boiling solvent to auxiliary is 1/0 to l/ 10 on a weight basis.Such auxiliary solvents can be readily removed from the high-boilingsolvent, for example, by air-drying a chilled, noodled dispersion or bycontinuous water washing. Several of such highboiling solvents andauxiliary solvents utilized for incorporating dye developers aredescribed in French Pat. No. 1,313,765. The dye developers can also beincorporated into vehicles soluble in organic solvents which are alsosolvents for the dye developer. Likewise, other incorporating techniquesfor the dye developer such as ball-milling can be utilized.

The photographic elements of the. invention desirably contain auxiliarydeveloping agents, in addition to catechols, such as colorlesssubstantially water-insoluble hydroquinone derivatives, e.g., thosedisclosed in French Pat. No. 1,313,086.

Such auxiliary developing agents can be incorporated in the silverhalide emulsion layers, in overcoat layers, in inter-layers or in otherlayers of the element.

The silver halide emulsions utilized in preparing the photographicelements of the invention are more generally the conventionalnegative-type developing-out emulsions, positive transfer imagesresulting from such emulsions. However,

reversal emulsions such as solarized emulsions and emulsions that formlatent images predominantly internal to the silver halide grains asdescribed in US. Pat. No. 2,592,250, can also be used, negative transferimages resulting from such emulsions. Typical suitable silver halidesinclude silver chloride, silver bromide, silver bromoiodide, silverchloroiodide, silver chlorobromoiodide, etc. Useful'sensitizers arethose in Kennard Ser. No. 337,792, filed Jan. 15, 1964. Mixtures of morethan one of such silver halides can also be utilized. ln preparing suchsilver halide emulsions, a wide variety of hydrophilic organic colloidscan be utilized as the vehicle or carrier. I prefer to utilize gelatinas the hydrophilic colloid or carrier material although such material aspolyvinyl alcohol and its water-soluble derivatives and copolymers,water-soluble copolymers such as polyacrylamide, imidizedpolyacrylamide,etc., or polymerized vinyl compounds such as those disclosed in US. Pat.Nos. 3,142,568, 3,193,386, 3,062,674 and 3,220,844, and including thewater-insoluble polymers of alkyl acrylates and methacrylates, acrylicacid, sulfoalkyl acrylates or methacrylates and the like.

In the present photographic elements, the dye developers are disposedintegral with the element and contiguous to silver halide of each of thelight-sensitive silver halide emulsion layers. Such dye developers canbe incorporated directly in the light-sensitive silver halide emulsionlayers or in separate layers contiguous to the layers containing thesilver halide. The present photographic elements contain at least twodye image-forming units, each unit comprising a light-sensitive silverhalide emulsion and a dye developer contiguous to silver halide in theunit. Each dye image-forming unit is preferably spectrally sensitized torecord light that is substantially-complementary to the color of the dyedeveloper in the unit.

The various layers utilized in preparing the present photographicelements can be coated on a wide variety of transparent and opaquephotographic supports. Typical supports include cellulose nitrate film,cellulose acetate film, polyvinyl acetal film, polystyrene film,polyethylene terephthalate film, polyethylene film, polypropylene film,paper, polyethylenecoated paper, glass;

A wide variety of receiving sheets can be utilized to receive the dyedeveloper images from the present light-sensitive photographic elements.The sequestering agents used in the invention can be positioned in anyof the layers of the receiving sheet. Typical reception layers for dyedeveloper receiving sheets which are, or include, mordants for dyedevelopers, are such material as linear polyamides, proteins such asgelatin, polyvinyl pyrrolidones, poly-4-vinyl pyridine, polyvinylalcohol, polyvinyl salicylal, partially hydrolyzed polyvinyl acetate,methyl cellulose, regenerated cellulose, carboxymethyl cellulose andhydroxyethyl cellulose, or mixtures of such. These reception layers canbe coated on a suitable support of the type described above for thelight-sensitive elements of the invention and including transparent aswell as opaque supports. Also, receiving sheets that release acidicmaterial such as that derived from an acidic polymer or other acidiccompound at a controlled rate are as described in US. Pat. No. 2,584,030are particularly useful. Such acidic materials are typically positionedin layers on the receiving sheet below the dye developer receptionlayer, there suitably being a spacer layer between the acid layer andthe mordanting layer to control the release of acidic material. Suchacidic materials serve to neutralize residual portions of the alkalineactivator on the receiving sheet. A wide variety of nondiffusiblecationic or basic dye-mordanting compounds can be used in liquidpermeable reception layers including amines such as polymeric amines,quaternary ammonium compounds, quaternary phosphonium compounds andtertiary sulfonium compounds. Such mordants are nondiffusible in thealkaline processing composition and contain at least one hydrophobicballast group.

To facilitate a clean stripping away of the receiving sheet from thenegative element after the transfer of the dye developer images to thereceiving sheet, the receiving sheet can be prepared by superficiallyhardening with a nondifiusing hardener and a surfactant. For example, adye developer image receiving layer on a receiving sheet containingpoly-4- vinyl pyridine mordant in polyvinyl alcohol can be efficaciouslytreated with an oxyguar gum hardener solution containing a surfactantsuch as soidum cetyl sulfate or sodium N- methyl-N-oleoyl taurate.

Light-sensitive elements containing integral reception layers for dyedeveloper images can also be utilized. Such integral reception layerscan be coated beneath the emulsion and dye developer layers near thesupport. A stripping layer coated over the integral reception layer canbe used to facilitate the removal of the overcoated layers after thediffusion of the dye developer images to the reception layer.

The processing compositions or activators used to initiate developmentof the exposed light-sensitive elements of the invention are stronglyalkaline. Such processing compositions generally have a pH of at leastabout 12 or contain a least 0.01 N hydroxyl ion. Alkali metalhydroxides, such as sodium hydroxide, and potassium hydroxide, areadvantageously used in the composition for imparting such highalkalinity. However, volatile amines such as diethyl amine can also beused, such amines having the advantage of being volatilized from theprints to leave no residue of alkali. Such processing compositions aregenerally aqueous liquids or solutions, and when utilized in rupturablepods for in-camera processing, generally contain thickening agents suchas hydroxyethyl cellulose, particularly as described in U.S. Pat. No.3,266,894, or carboxymethyl cellulose. Onium compounds such as aredisclosed in U.S. Pat. No. 3,146,102 are preferably utilized in thealkaline processing composition. The described sequestering agents canalso be utilized in the alkaline processing compositions used in theprocesses of the invention.

Camera apparatus of the type useful for exposing and processing thesensitive elements of the invention have been described, for example, inU.S. Pat. No. 2,435,717. The processing of the subject photographicelements can also be effected outside of camera apparatus by imbibingeither the receiving element or the negative element or both in thealkaline processing composition, and thereafter sandwiching together thetwo elements to allow the dye developer images to diffuse to thereceiving element.

in accordance with usual practice, the positioning of the dyeimage-forming units of the photographic elements of the invention can bevaried. ln three-color systems, it is preferred to utilize the cyan dyeimage-forming unit most proximate to the support, the yellow dye-formingunit furthest from the support, the yellow dye image-fonning units. ltis also preferred to utilize the dye developers in the respective dyeimage-forming units in a separate underlying layer contiguous to thesilver halide emulsion layer. Likewise, it is preferred to utilize ineach dye image-forming unit a dye developer that is substantiallycomplementary in color to the color of light recorded by the silverhalide in the unit.

The following examples are included for a further undcrstanding of theinvention:

EXAMPLE 1 A photographic element, element 1,

prepared by coating successively the following layers on a subbedcellulose acetate film support:

Layer No.

l. Cyan Dye Developer Layer A coating of the cyan dye developer,5,8-dihydroxy-l ,4-bis[B-hydroquinonyl-a-methyl)ethylaminoI-anthraquinone, dissolved inN-n-butylacetanilide, dispersed in gelatin and coated on the support.

2. Red-sensitive Emulsion Layer A coating of a developing-out negativegelatino-silver bromoiodide emulsion sensitized to red light coated at acoverage of about 180 mg. of silver per square foot.

3. Gelatin Layer A gelatin layer is coated over the red-sensitiveemulsion layer.

4. Sodium Alginate Layer A coating of sodium alginate at a coverage ofabout 30 mg. per square foot is applied over the gelatin layer.

5. Magenta Dye Developer Layer A coating of the magenta dye developer,4-isopropoxy-2-l p- (B-hydroquinonylethyl)-phenylazo]-1-naphthol,dissolved in N-n-butylacetanilide, dispersed in gelatin and containingabout 2 mg. 4'-methylphenyl-hydroquinone and about 15 mg. of calciumchloride per square foot is coated over layer 4. the calcium chloridereacts with the sodium alginate in layer 4 to form a calcium alginatesalt barrier layer between the two layers.

6. Green-Sensitive Emulsion Layer A coating of a developing-out negativegeIatino-silver bromoiodide emulsion sensitized to green light is thencoated at a coverage of about 1 10 mg. of silver per square foot.

7. lnterlayer A gelatin layer is coated containing about 5 mg. persquare foot 4-methylphenylhydro quinone.

8. Sodium Alginate Layer Sodium alginate is coated at about 15 mg. persquare foot.

9. Yellow Dye Developer Layer A coating of the yellow dye developer,l-phenyI-S-N-n-hexylcarboxamide-4-[p-(2,5'-dihydroxyphenethyl)-phenylazo]- S-pyrazolone, dissolved inditetrahydrofurfuryl adipate, dispersed in gelatin and containing about2 mg. of 4'- methylphcnylhdeydroquinone and about 10 mg. of calciumchloride per square foot. The calcium chloride reacts with the sodiumalginate in the adjacent layer to form a calcium alginate salt barrierbetween the two layers.

10. Blue-Sensitive Emulsion Layer A developing-out negativegelatino-silver bromoiodide emulsion that is inherently sensitive toblue light is coated at a coverage of about 70 mg. of silver per squarefoot, the emulsion also containing about 25 mg.4'-methylphenyl-hydroquinone per square foot.

1 l. Overcoat Layer A gelatin layer is coated over layer 10.

The photographic element described above is the control. Anotherelement, element 2, is prepared exactly the same as element 1, thecontrol, except, except that element 2 also contains 20 mg. per squarefoot 4-phenylcatechol in layer no. 3. Another element, element 3, isexactly the same as element 1, the control, except that element 3 alsocontains 30 mg. per square foot 4-phenylcatechol in layer no. 7. Thephotographic elements obtained are each exposed through a 0.3 densityincrement color step wedge in an intensity scale sensitometerone-fiftieth inches to a 500 watt positive lamp using a blue coloredfilter that absorbs some red light to convert the tungsten exposure todaylight color balance, and processed with a processing solutiondisposed in a processing pod and having a composition like thatdescribed by Land in example 7 of U.S. Pat. No. 3,362,821 issued Jan. 9,1968. The exposed film is processed at a gap of 0.004 inch(corresponding to the thickness of the activator layer) for a period of60 seconds in contact with a color receiving sheet. The receiving sheetis a cellulose acetate butyrate subbed paper support carrying in thefollowing order:

1) a polymeric acid layer for pH control,

2) a polyvinyl alcohol spacer layer 3) a mordant layer comprisingpoly-4-vinyl pyridine and polyvinyl alcohol, and

4) a polyvinyl alcohol protective layer.

The reflection densities of the graduated scales of the transferred dyeimages on the receiving sheets are determined. Table A below shows theneutral scale maximum density for the red (cyan dye developer), green(magenta dye developer and blue (yellow dye developer). Magenta drop-offis a measure of the amount of density of the magenta dye developer imageresulting from the magenta developer developing in the red-sensitiveemulsion layer. it is determined by substracting the magenta density inthe red scale from the magenta Dmax. The magenta density in the redscale is measured at a point 0.8 log E greater exposure than the log Evalue of a 0.6 density in the neutral scale. Yellow drop-off is ameasure of the-amount of desaturation of the. yellow dye developer imageresulting from the yellow dye developer developing in'the greensensitive emulsion layer. It is determined by subtracting the yellowdensity in the green scale from yellow Dmax. Yellow density in the greenscale is measured at a point 0.8 log E slower than the log E value of a0.6 density in the neutral scale. Table A shows the increased cyan dyedeveloper image saturation, without undesirable increases in magenta andyellow drop off, due to the use of a catechol in accordance with theinvention.

It will be observed that the use of catechol esults in ljghred 94EXAMPLE 3 10 contains, respectively, sufficient 4-phenyl-catechol toprovide coverages of 0.32 and 0.64 millimoles of 4-phenylcatcchol persquare foot. The treated negatives are then exposed and processedexactly as described .in example I. the results are shown in table Cbelow.

TABLE mll. mln. Relative speed Element Remarks: negative treated with-No. Red Green Blue Red Green Blue Red Green Blue 1. 31 2. 04 2. 25 22 2627 100 100 100 Acstronltlle. 1. 60 2. 04 2. 25 20 .26 28 -110 126 97 0.2m. 4-phenyl-cateehol. 1. 68 2. 01 2. 22 20 26 28 100 118 82 0.4 m.4-phenyleateehol.

'Speedteken at D=0.8.

Dmax, without sacrificing color purity (as indicated by the smallincreases in magenta and yellow drop-off). Similar results are obtainedwith 4-phenylcatechol in element 2 is replaced with 20 mg. of catechol;3-isopropylcatechol; 4-tertbutylcatechol; p-chlorocatechol or4-phenoxycatechol. Essentially the same results are obtained as withelement 3 when the calcium'alginate barrier layers are replaced withazirconium gelatinate'layer; a chromium alginate layer; a calciumpectinate layer or a lead-carboxymethy cellulose layer.

A photographic element, element 4, is prepared exactly the same aselement 1 of example 1, with the following exceptions:

No 4-methylphenylhydroquinone in layer 5;

Layer 7contains 140 mg. of gelatin and mg. of 4'-methylphenylhydroquinone per square foot;

Layer 8 (sodium alginate) is omitted;

Layer 9 contains no calcium chloride or 4'-methylphenylhydroquinone;

Layer 10 contains 12 mg. of 4-methylphenylhydroquinone. Element 4 is acontrol. Element 5 is prepared in the same manner except that layer 1also contains mg. of 4-phenylcatechol per square foot. The elements areexposed and processed exactly the same as in example I. The results areshown in table B.

TABLE B Element 4-Phenyl- Neutral Scale Dmax. Magenta No. catechol RedGreen Blue Drop-Off 4 None 1.28 2.02 1.47 1.13 5 20 mg. in Layer l L49L98 L44 017 As will be observed in the above table, increased cyan dyedeveloper saturation is obtained without undue loss in purity when thecatechol incorporated in the dye developer layer it- 75 self, ratherthan in an interlayer.

As shown by the above date, the 4-phenylcatechol treated negatives giveprints with decidedly more red density than the control. Similar resultsare obtained when the 4-phenylcatechol is contained in the receivingsheet rather than in an activator solution.

The invention has been described in detail with particular reference tocertain preferred embodiments thereof, but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention as described hereinabove and as defined in the appendedclaims.

lclaim: V

1. In a photographic element comprising a support having coated thereonat least two dye image-forming units with an alkali-permeable,water-insoluble salt ,stratum positioned between at least two of saiddye image-forming units, said dye image-forming units comprising asilver halide emulsion layer and a dye developer contiguous to silverhalide of said emul sion, and said salt stratum comprising analkali-permeable, water-insoluble salt of a polyvalent metal and afilm-forming, alkali-permeable, water-soluble polymer having freecarboxylic acid groups, said salt stratum being less permeable to dyedevelopers comprising said dye image-forming units in aqueous alkalinesolution than said water-soluble polymer used to prepare said saltstratum, the improvement which comprises having coated on the saltstratum side of the photographic element a material that is a chelatingagent for said polyvalent metal, the chelating function of said materialbeing destroyed imagewise in just exposed area as a function ofdevelopment.

2. A photographic element as defined by claim I wherein said material isan auxiliary developer.

3. In a photographic element comprising a support having coated thereonat least two dye image-forming units with an alkali-permeable,water-insoluble salt stratum positioned between at least two of said dyeimage-forming units, said dye image-fanning units comprising a silverhalide emulsion layer and a dye developer contiguous to silver halide ofsaid emulsion, and said salt stratum comprising an alkali-permeable,water-insoluble salt of an alkaline earth metal and a film-forming,alkali-permeable, water-soluble polymer having free carboxylic acidgroups, said salt stratum being less permeable to dye developerscomprising said dye image-forming units in aqueous alkaline solutionthan said water-soluble polymer used to prepare said salt stratum, theimprovement which comprises having coated on the salt stratum side ofthe photographic element a catechol which develops silver halide and isa chelating agent for said polyvalent metal.

4. A photographic element as defined by claim 3 wherein the salt stratumis calcium alginate.

5. A photographic element as defined by claim 3 wherein the catechol hasthe formula:

wherein R R,, R and R, are each selected from the group consisting ofhydrogen, hydroxyl, halogen, carboxy, aryloxy, alkyl, aryl and, R, andR, and R when taken together with the carbon atoms to which they areattached, represent the atoms to complete a cycloalkyl group.

6. A photographic element as defined by claim 4 wherein the catechol is4-phenylcatechol.

7. A photographic element comprising superposed on a photographicsupport three dye image-forming units in layers capable of recordingred, green and blue light respectively, the dye image-forming unitrecording blue light being furthest from the support and the dyeimage-fonning unit recording red light being most proximate to thesupport, and an alkali permeable, waterinsoluble stratum of calciumalginate positioned between each of the said image-forming units, saiddye image-forming units comprising a gelatino-silver halide emulsionlayer and an underlying contiguous layer containing a dye developersubstantially complementary in color to the color of light recorded inthe contiguous silver halide emulsion layer, and a catechol whichdevelops silver halide and is a chelating agent for calcium ions beingpositioned between said support and said stratum of calcium alginate,said catechol being present in an amount sufficient to increase thepermeability of said stratum in just the unexposed areas.

8. A photographic element comprising superposed on a photographicsupport three dye image-forming units in layers capable of recordingred, green and blue light respectively, the dye image-fonning unitrecording blue light being furthest from the support and the dyeimage-forming unit recording red light being most proximate to thesupport, and an alkaliperrneable, water-insoluble stratum of calciumalginate positioned between the said image-forming units recording redand green light, said dye image-forming units comprising agelatino-silver halide emulsion layer and an underlying contiguous layercontaining a dye developer substantially complementary in color to thecolor of light recorded in the contiguous silver halide emulsion layer,and a catechol which develops silver halide and is a chelating agent forcalcium ions being positioned between said support and said stratum ofcalcium alginate, said catechol being present in an amount sufficient toincrease the permeability of said stratum in just the unexposed areas.

9. In the processing of an imagewise exposed photographic elementcomprising a support having coated thereon at least two dyeimage-forming units with an alkali-permeable, waterinsoluble saltstratum positioned between at least two of said dye image-fonning units,said dye image-forming units comprising a silver halide emulsion layerand a dye developer contiguous to silver halide of said emulsion, andsaid salt stratum comprising an alkali-permeable, water-insoluble saltof a polyvalent metal and a film-forming alkali-permeable, watersolublepolymer having free carboxylic aid groups, said salt stratum being lesspermeable to dye developers comprising said dye image-forming units inaqueous alkaline solution than said water-soluble polymer used toprepare said salt stratum, which comprises treating the photographicelement with an alkaline processing liquid, developing latent images inthe regions of exposure of the silver halide emulsion layers and therebyimmobilizing dye developers in said regions of exposure, dye developersin undeveloped regions diffusing imagewise in register to a receptionlayer for dye developer images, the improvement which comprises carryingout said treating of the photographic element in the presence of amaterial that is a chelating agent for said polyvalent metal, thechelating function of said material being destroyed imagewise in justexposed areas as a function of development.

10. The process as defined in claim 9 wherein said material is anauxiliary developer coated in a layer on the salt stratum side of thephotographic element.

11. ln the processing of an imagewise exposed photographic elementcomprising a support having coated thereon at least two dyeimage-forming units with an alkali-permeable, waterinsoluble saltstratum positioned between at least two of said dye image-forming units,said dye image-forming units comprising a silver halide emulsion layerand a dye developer contiguous to silver halide of said emulsion, andsaid salt stratum comprising an alkali-permeable, water-insoluble saltof an alkaline earth metal and a film-forming alkali-permeable,watersoluble polymer having free carboxylic acid groups, said saltstratum being less permeable to dye developers comprising said dyeimage-forming units in aqueous alkaline solution than said water-solublepolymer used to prepare said salt stratum, which comprises treating thephotographic element with an alkaline processing liquid, developinglatent images in the regions of exposure of the silver halide emulsionlayers and thereby immobilizing dye developers in said regions ofexposure, dye developers in undeveloped regions diffusing imagewise inregister to a reception layer for dye developer images, the improvementwhich comprises carrying out said treating of the photographic elementin the presence of a catechol which develops silver halide and is achelating agent for said olyvalent metal.

12. T e process as defined in claim 11 wherein the catechol wherein R RR and R are each selected from the group consisting of hydrogen,hydroxyl, halogen, carboxy, aryloxy, alkyl, aryl and, R and R or R and Rwhen taken together with the carbon atoms to which they are attached,represent the atoms to complete a cycloalkyl group.

16. The process as defined in claim 11 wherein the catechol is4-phenylcatechol.

2. A photographic element as defineD by claim 1 wherein said material isan auxiliary developer.
 3. In a photographic element comprising asupport having coated thereon at least two dye image-forming units withan alkali-permeable, water-insoluble salt stratum positioned between atleast two of said dye image-forming units, said dye image-forming unitscomprising a silver halide emulsion layer and a dye developer contiguousto silver halide of said emulsion, and said salt stratum comprising analkali-permeable, water-insoluble salt of an alkaline earth metal and afilm-forming, alkali-permeable, water-soluble polymer having freecarboxylic acid groups, said salt stratum being less permeable to dyedevelopers comprising said dye image-forming units in aqueous alkalinesolution than said water-soluble polymer used to prepare said saltstratum, the improvement which comprises having coated on the saltstratum side of the photographic element a catechol which developssilver halide and is a chelating agent for said polyvalent metal.
 4. Aphotographic element as defined by claim 3 wherein the salt stratum iscalcium alginate.
 5. A photographic element as defined by claim 3wherein the catechol has the formula:
 6. A photographic element asdefined by claim 4 wherein the catechol is 4-phenylcatechol.
 7. Aphotographic element comprising superposed on a photographic supportthree dye image-forming units in layers capable of recording red, greenand blue light respectively, the dye image-forming unit recording bluelight being furthest from the support and the dye image-forming unitrecording red light being most proximate to the support, and analkali-permeable, water-insoluble stratum of calcium alginate positionedbetween each of the said image-forming units, said dye image-formingunits comprising a gelatino-silver halide emulsion layer and anunderlying contiguous layer containing a dye developer substantiallycomplementary in color to the color of light recorded in the contiguoussilver halide emulsion layer, and a catechol which develops silverhalide and is a chelating agent for calcium ions being positionedbetween said support and said stratum of calcium alginate, said catecholbeing present in an amount sufficient to increase the permeability ofsaid stratum in just the unexposed areas.
 8. A photographic elementcomprising superposed on a photographic support three dye image-formingunits in layers capable of recording red, green and blue lightrespectively, the dye image-forming unit recording blue light beingfurthest from the support and the dye image-forming unit recording redlight being most proximate to the support, and an alkali-permeable,water-insoluble stratum of calcium alginate positioned between the saidimage-forming units recording red and green light, said dyeimage-forming units comprising a gelatino-silver halide emulsion layerand an underlying contiguous layer containing a dye developersubstantially complementary in color to the color of light recorded inthe contiguous silver halide emulsion layer, and a catechol whichdevelops silver halide and is a chelating agent for calcium ions beingpositioned between said support and said stratum of calcium alginate,said catechol being present in an amount sufficient to increase thepermeability of said stratum in just the unexposed areas.
 9. In theprocessing of an imagewise exposed photographic element comprising asupport having coated thereon at least two dye image-forming units withan alkali-permeable, water-insoluble salt stratum positioned between atleast two of said dye image-forming units, said dye image-forming unitscomprising a silver halide emulsion layer and a dye deVeloper contiguousto silver halide of said emulsion, and said salt stratum comprising analkali-permeable, water-insoluble salt of a polyvalent metal and afilm-forming alkali-permeable, water-soluble polymer having freecarboxylic aid groups, said salt stratum being less permeable to dyedevelopers comprising said dye image-forming units in aqueous alkalinesolution than said water-soluble polymer used to prepare said saltstratum, which comprises treating the photographic element with analkaline processing liquid, developing latent images in the regions ofexposure of the silver halide emulsion layers and thereby immobilizingdye developers in said regions of exposure, dye developers inundeveloped regions diffusing imagewise in register to a reception layerfor dye developer images, the improvement which comprises carrying outsaid treating of the photographic element in the presence of a materialthat is a chelating agent for said polyvalent metal, the chelatingfunction of said material being destroyed imagewise in just exposedareas as a function of development.
 10. The process as defined in claim9 wherein said material is an auxiliary developer coated in a layer onthe salt stratum side of the photographic element.
 11. In the processingof an imagewise exposed photographic element comprising a support havingcoated thereon at least two dye image-forming units with analkali-permeable, water-insoluble salt stratum positioned between atleast two of said dye image-forming units, said dye image-forming unitscomprising a silver halide emulsion layer and a dye developer contiguousto silver halide of said emulsion, and said salt stratum comprising analkali-permeable, water-insoluble salt of an alkaline earth metal and afilm-forming alkali-permeable, water-soluble polymer having freecarboxylic acid groups, said salt stratum being less permeable to dyedevelopers comprising said dye image-forming units in aqueous alkalinesolution than said water-soluble polymer used to prepare said saltstratum, which comprises treating the photographic element with analkaline processing liquid, developing latent images in the regions ofexposure of the silver halide emulsion layers and thereby immobilizingdye developers in said regions of exposure, dye developers inundeveloped regions diffusing imagewise in register to a reception layerfor dye developer images, the improvement which comprises carrying outsaid treating of the photographic element in the presence of a catecholwhich develops silver halide and is a chelating agent for saidpolyvalent metal.
 12. The process as defined in claim 11 wherein thecatechol is coated in a layer on the salt stratum side of thephotographic element.
 13. The process as defined in claim 11 wherein thecatechol is present in the alkaline processing liquid.
 14. The processas defined in claim 11 wherein the salt stratum is calcium alginate. 15.The process as defined in claim 11 wherein the catechol has the formula:16. The process as defined in claim 11 wherein the catechol is4-phenylcatechol.